678 THE RESPIRATION AND [pt. m 



The matter was then taken up by Parnas & Krasinska, who 

 pubHshed their resuks in 1921. On many points their work led them 

 to other conclusions than those of Bialascewicz & Bledovski, for they 

 could not find respiratory quotients corresponding to the combustion 

 of fat, and they did not obtain perfectly regular curves for oxygen 

 consumption. They used as their principal method the Barcroft 

 manometer technique, and their experiments seem to have been 

 better carried out than those of any of their predecessors. The/ 

 worked on the eggs of three species of amphibia, Rana temporaria, 

 Bufo variabilis, and Rana esculenta. The experiments included more 

 elaborate controls than had before been made, e.g. it was ascertained 

 that the presence or absence of the gelatinous coverings made no 

 difference to the respiration of the embryos in any stage, and that 

 the development was normal in all the experiments, irrespective of 

 the partial pressure of oxygen within wide limits. After 70 hours 

 at 15°, the embryos which had been in a pure oxygen atmosphere 

 were slightly more advanced than those which had been in the air, 

 but at 11° this difference was hardly noticeable, although the dif- 

 fusion of the gases would hardly be affected at all by such a change 

 of temperature. Experiments were carried through at the higher 

 temperature when it was desired to follow a long period, but at 

 the lower temperature when the details of the early stages were under 

 examination. 



Parnas & Krasinska found that the oxygen consumption of Bufo 

 vulgaris eggs at 14° in air before fertilisation was o-og c.mm. per Ggg 

 per hour, but after fertilisation 0-34 c.mm. per Qgg per hour, a rise 

 of about four times, rather more than had been found by Bialasce- 

 wicz & Bledovski on the frog. In pure oxygen the rise occurred just 

 the same, and to the same extent, though the absolute figures were 

 higher. Parnas & Krasinska regarded the unfertilised egg as a dying 

 cell, in view of the fact that, at a definite time after laying, it loses 

 its capacity for being fertilised, and they suggested that the asphyxial 

 conditions which had been shown by the earlier workers to hold 

 in the oviduct were important as conserving the eggs in a state of 

 suspension, it being impossible for any great amount of metabolism 

 to go on in them before laying. 



Typical graphs of Parnas & Krasinska's results are given in 

 Figs. 130, 131 and 132. The first of these shows the oxygen uptake 

 of the eggs of Rana temporaria for the first 1 00 hours after fertilisation ; 



